Experimental Study On Performance Of Fly Ash And Polypropylene Fiber Modified Frost-resistant Concrete

In order to deal with the problem of frost damage in concrete in northern China,the addition of air entraining agent can significantly improve the frost resistance of concrete and make it become frost-resistant concrete.However,the incorporation of air entraining agent can decrease concrete strength.Therefore,in this paper,the strength of air-entrained concrete is improved by adding fly ash and polypropylene fiber.At the same time,the influence of fly ash and polypropylene fiber on frost resistance of air-entrained concrete is studied.The tests in this paper are divided into two groups according to curing age.The ordinary concrete with a curing age of 28 days is separately blended with 0.02%,0.04%,0.06%air entraining agent and the ordinary concrete with a curing age of 56 days is separately blended with 0.01%,0.04%,0.08%air entraining agent to determine relationship between air entraining agent content and gas content;add 10%,20%,30%fly ash and 0.5%,1.0%polypropylene fiber to air-entrained concrete separately with curing 28 days,and add 5%,15%,25%fly ash and 0.6%,0.9%,1.5%polypropylene fiber respectively to air-entrained concrete with curing 56 days.The effect of fly ash and polypropylene fiber on air-entrained concrete strength is studied through basic mechanical tests,and the effect of fly ash and polypropylene fiber on frost resistance of air-entrained concrete is studied through frost resistance test.It is ensure that add fly ash and polypropylene fiber will not affect original frost resistance when increases air-entrained concrete strength.Finally,the influence of different materials on the appearance damage of concrete after freezing and thawing is analyzed.Through the above experimental study,following conclusions are obtained.The gas content of concrete increases with increasing air entraining agent's amount,the compressive strength and flexural strength decrease with increasing air entraining agent's amount;proper amount of air entraining agent can improve concrete frost resistance.Fly ash can increase compressive strength of air-entrained concrete,but it can't increase flexural strength;Although fly ash has certain negative impact on frost resistance,but the impact is small and can be considered within the allowable range.Polypropylene fiber can improve compressive strength of air-entrained concrete;under proper vibration,increase polypropylene fiber content can slightly increase flexural strength of air-entrained concrete;polypropylene fiber almost has no negative impact on frost resistance of air-entrained concrete.Therefore,appropriate amount of fly ash and polypropylene fiber can increase air-entrained concrete strength under the premise of ensuring original frost resistance.